The present invention relates to the field of pressure vessels. It finds particular application to sterilizers or autoclaves for steam sterilization of medical and laboratory instruments and other equipment. It is to be appreciated, however, that the present invention may also find application in conjunction with other types of sterilizing, disinfecting, and sanitizing apparatus.
Steam sterilizers are currently used in hospitals, doctors offices, dentists offices, and laboratories to sterilize medical and dental instruments, laboratory equipment, production equipment, manufactured products, and other equipment. Sterilizers are made in different sizes for different applications from 6-10 liter small size sterilizers which fit a few trays of instruments and can be used in a small doctor's or dentist's office to large sterilizers which are the size of a small room. In between these two extremes are sterilizer sizes typically used in hospitals to sterilize everything used with patients, including linens, bedding, bed pans, as well as medical instruments.
Steam sterilizers generally include an inner shell which defines a sterilization chamber into which the articles to be sterilized are placed. The sterilizers may also include an outer jacket surrounding the inner shell and providing a space between the inner shell and outer jacket for injection of steam. The sterilizers are operated by placing the articles to be sterilized inside the chamber and preheating the chamber by pumping saturated steam into the jacket space between the outer jacket and the inner shell. Once the jacket is charged with steam, saturated steam is injected into the sterilization chamber. Commonly, in hospital applications, steam is piped from inside the jacket space into the sterilization chamber for sterilizing the chamber contents.
At the end of the sterilization cycle, the steam is pumped out of the chamber and the chamber evacuated to a pressure below atmospheric pressure to remove any moisture remaining in the chamber or on the sterilized articles.
Small and medium size sterilizers are generally either cylindrical or rectangular in shape. There is a trade off between usable space and manufacturing cost between cylindrical and rectangular sterilizers. The cylindrical sterilizers are less expensive to manufacture due to their shape which meets stress/strain requirements for pressurization without additional reinforcing structures surrounding the cylinder. However, cylindrical sterilizers include some amount of unusable space because the items placed in the sterilizer are generally rectangular. In contrast, rectangular sterilizers provide more usable space than cylindrical sterilizers for the same size of foot print. The cost of rectangular sterilizers is generally greater than that of cylindrical sterilizers of the same size due to reinforcement which is needed particularly at the corners of the rectangular sterilizer shell to provide sufficient shell strength.
The present invention contemplates a new and improved sterilizer for addressing the capacity versus cost tradeoff of known sterilizers.